Many assume that people who commit terrorist attacks in the name of Islam are religious zealots. Actually, many Muslim radicals were not particularly religious at the get-go. Indeed, a substantial number of Isis sympathizers are converts to Islam - hardly lifelong devotees.

If not religion, then, what is to blame?

Researchers have long studied the motivations of terrorists, with psychologist Arie Kruglanski proposing a particularly compelling theory: people become terrorists to restore a sense of significance in their lives, a feeling that they matter. Extremist organizations like Isis are experts at giving their recruits that sense of purpose, through status, recognition, and the promise of eternal rewards in the afterlife.

My own survey work supports Kruglanski's theory. I find that American Muslims who feel a lack of significance in their lives are more likely to support fundamentalist groups and extreme ideologies.

What we really need to know now is, what sets people on this path? How do people lose their sense of purpose?

My research reveals one answer: the more my survey respondents felt they or other Muslims had been discriminated against, the more they reported feeling a lack of meaning in their lives. Respondents who felt culturally homeless - not really American, but also not really a part of their own cultural community - were particularly jarred by messages that they don't belong. Yet Muslim Americans who felt well integrated in both their American and Muslim communities were more resilient in the face of discrimination.

The Florida mass shooter's justification for lying about knowing the Boston terrorists (the reason for his earlier FBI investigation), teasing from work colleagues for being Muslim, could well have contributed to his radicalisation (on top of being a mess).